1. Field of the Disclosure
The present disclosure relates to a switching mode power supply, and more particularly, to a switching mode power supply for switching an input voltage to have an optimum efficiency according to the size of a load.
2. Description of Related Art
In general, a switching mode power supply apparatus is an apparatus for converting an alternating current power source supplied from a commercial power source into a direct current power source to supply power suitable to the capacity used for various home appliances. For example, a refrigerator may use a switching mode power supply apparatus based on a fly-back scheme.
For the most widely used switching operation schemes, the fly-back switching mode power supply apparatus may use a PWM scheme having a fixed switching frequency and a quasi-resonant scheme having a frequency varied based on the size of a load. In particular, the quasi-resonant scheme has a frequency varied by increasing the frequency when the load is low, and reducing the frequency when the load is high.
The existing switching mode power supply apparatus switches a voltage induced to a secondary side of a transformer by selecting either one of the foregoing two schemes, and thus, for example, with a product with a large load change such as a refrigerator, the efficiency of consumption power can be high only for a specific region of the load. In other words, a power circuit may be implemented to drive a switching operation in either one of the PWM and quasi-resonant scheme, thereby having a problem in which high efficiency cannot be attained for the entire load regions.